[CRIU] [PATCH 2/2] mem: Don't assume guard page is returned in procfs with new kernels

[Cyrill Gorcunov]

On Tue, Jun 20, 2017 at 03:34:38PM +0200, Oleg Nesterov wrote:
> 
> Hmm, confused. After this kernel patch unmap_guard_pages() makes no sense, it
> should not be called. I think you see the failures exactly because you need to
> fix more GROWSDOWN checks?

Yes. I think so. We still do +|- PAGE_SIZE for stack which I've just
cleaned out and we're running tests by now.

> And. Please forget about the kernel patch for the moment. Lets suppose that we
> disable all this logic unconditionally (to remind, this is what we will probably
> do) and run criu with the old kernel.
> 
> Now, iiuc criu will mostly work. Usually there is nothing in the hidden guard
> page. But most probably you have some test-cases which test this functionality,
> say, a test-case can munmap the guard page, then check that the whole stack was
> restored correctly?

I guess we're failing in one of the tests for exactly this reason.

> IOW, could you tell us which test-cases should certainly fail if we remove or
> disable the stack-guard-page hacks in criu? So that we can distinguish (I mean
> ignore ;) these failures from the real problems?

test/zdtm/static/grow_map.c may fail

	Cyrill